Abstract
This paper aims to determine cost optimality between heating, ventilation and air conditioning (HVAC) systems operating with air to water heat pumps (AWHP) and water to water heat pumps (WWHP). The analysis is performed for a certain number of heat pump units with fixed and variable capacity made by four manufacturers available on European market. Simulations are performed in Trnsys software. The results show that heat pump partial load efficiency should not be neglected in analysis of application while the difference in energy consumption and costs can be up to 17%. The requirement for performing analysis on a wider range of units is indicated, especially when heat pump systems with different sources are considered. HVAC system with AWHP units with capacity control is a cost optimal solution for case study nursery building operating on the Croatian coast. The application of the photovoltaic (PV) array sized to cover nonrenewable part of electricity consumed in HVAC system has a return period of 12 years. It is determined that seasonal efficiency indicators from relevant European database do not support unit operation.
Highlights
Heat pumps represent a promising solution to achieve cost optimal nearly zero energy building [1,2,3,4,5,6]
Heat pump electricity consumption is calculated as a function of performance coefficient of heat pump, coefficient of performance (COP) for heating and energy efficiency ratio (EER) for cooling
Coefficient of performance (COP or EER) at partial load can be estimated using the partial load factor (PLF), which is applied to the performance coefficient determined for operation at full capacity
Summary
Heat pumps represent a promising solution to achieve cost optimal nearly zero energy building (nZEB) [1,2,3,4,5,6]. Energy efficiency of heat pump strongly depends on heat source temperature (ambient air, ground water, solid soil, or chilled water) and heat sink temperature (e.g., temperature in heating system, domestic hot water (DHW) temperature or cooling water temperature). Operating parameters and efficiency of the heat pump constantly change during the operation and adapt to temperatures of heat source and heat sink, while the control system changes the compressor and unit capacity. Waddicor et al [9] determined that the control strategy has the greatest impact on the overall reduction in efficiency due to short device operation. These authors determined minimum device operating time of 15–20 min to avoid the reduction in efficiency. The improvement can be achieved by increasing the water accumulation volume in the case of an indirect system
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